Index: head/share/man/man9/Makefile
===================================================================
--- head/share/man/man9/Makefile
+++ head/share/man/man9/Makefile
@@ -669,7 +669,8 @@
 	condvar.9 cv_wait_unlock.9 \
 	condvar.9 cv_wmesg.9
 MLINKS+=config_intrhook.9 config_intrhook_disestablish.9 \
-	config_intrhook.9 config_intrhook_establish.9
+	config_intrhook.9 config_intrhook_establish.9 \
+	config_intrhook.9 config_intrhook_oneshot.9
 MLINKS+=contigmalloc.9 contigfree.9
 MLINKS+=casuword.9 casueword.9 \
 	casuword.9 casueword32.9 \
Index: head/share/man/man9/config_intrhook.9
===================================================================
--- head/share/man/man9/config_intrhook.9
+++ head/share/man/man9/config_intrhook.9
@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 24, 2006
+.Dd August 10, 2017
 .Dt CONFIG_INTRHOOK 9
 .Os
 .Sh NAME
@@ -35,10 +35,13 @@
 but before root is mounted
 .Sh SYNOPSIS
 .In sys/kernel.h
+.Vt typedef void (*ich_func_t)(void *arg);
 .Ft int
 .Fn config_intrhook_establish "struct intr_config_hook *hook"
 .Ft void
 .Fn config_intrhook_disestablish "struct intr_config_hook *hook"
+.Ft void
+.Fn config_intrhook_oneshot "ich_func_t func" "void *arg"
 .Sh DESCRIPTION
 The
 .Fn config_intrhook_establish
@@ -51,6 +54,18 @@
 .Fn config_intrhook_disestablish
 function removes the entry from the hook queue.
 .Pp
+The
+.Fn config_intrhook_oneshot
+function schedules a function to be run as described for
+.Fn config_intrhook_establish ;
+the entry is automatically removed from the hook queue
+after that function runs.
+This is appropriate when additional device configuration must be done
+after interrupts are enabled, but there is no need to stall the
+boot process after that.
+This function allocates memory using M_WAITOK; do not call this while
+holding any non-sleepable locks.
+.Pp
 Before root is mounted, all the previously established hooks are
 run.
 The boot process is then stalled until all handlers remove their hook
@@ -71,8 +86,8 @@
 .Bd -literal
 struct intr_config_hook {
 	TAILQ_ENTRY(intr_config_hook) ich_links;/* Private */
-	void	(*ich_func)(void *arg);		/* function to call */
-	void	*ich_arg;			/* Argument to call */
+	ich_func_t	ich_func;		/* function to call */
+	void		*ich_arg;		/* Argument to call */
 };
 .Ed
 .Pp
Index: head/sys/kern/subr_autoconf.c
===================================================================
--- head/sys/kern/subr_autoconf.c
+++ head/sys/kern/subr_autoconf.c
@@ -43,6 +43,7 @@
 #include <sys/kernel.h>
 #include <sys/linker.h>
 #include <sys/lock.h>
+#include <sys/malloc.h>
 #include <sys/mutex.h>
 #include <sys/systm.h>
 
@@ -63,6 +64,27 @@
 static void run_interrupt_driven_config_hooks(void);
 
 /*
+ * Private data and a shim function for implementing config_interhook_oneshot().
+ */
+struct oneshot_config_hook {
+	struct intr_config_hook 
+			och_hook;		/* Must be first */
+	ich_func_t	och_func;
+	void		*och_arg;
+};
+
+static void
+config_intrhook_oneshot_func(void *arg)
+{
+	struct oneshot_config_hook *ohook;
+
+	ohook = arg;
+	ohook->och_func(ohook->och_arg);
+	config_intrhook_disestablish(&ohook->och_hook);
+	free(ohook, M_DEVBUF);
+}
+
+/*
  * If we wait too long for an interrupt-driven config hook to return, print
  * a diagnostic.
  */
@@ -181,6 +203,22 @@
 		/* XXX Sufficient for modules loaded after initial config??? */
 		run_interrupt_driven_config_hooks();	
 	return (0);
+}
+
+/*
+ * Register a hook function that is automatically unregistered after it runs.
+ */
+void
+config_intrhook_oneshot(ich_func_t func, void *arg)
+{
+	struct oneshot_config_hook *ohook;
+
+	ohook = malloc(sizeof(*ohook), M_DEVBUF, M_WAITOK);
+	ohook->och_func = func;
+	ohook->och_arg  = arg;
+	ohook->och_hook.ich_func = config_intrhook_oneshot_func;
+	ohook->och_hook.ich_arg  = ohook;
+	config_intrhook_establish(&ohook->och_hook);
 }
 
 void
Index: head/sys/sys/kernel.h
===================================================================
--- head/sys/sys/kernel.h
+++ head/sys/sys/kernel.h
@@ -400,13 +400,16 @@
 #define	TUNABLE_STR_FETCH(path, var, size)			\
 	getenv_string((path), (var), (size))
 
+typedef void (*ich_func_t)(void *_arg);
+
 struct intr_config_hook {
 	TAILQ_ENTRY(intr_config_hook) ich_links;
-	void	(*ich_func)(void *arg);
-	void	*ich_arg;
+	ich_func_t	ich_func;
+	void		*ich_arg;
 };
 
 int	config_intrhook_establish(struct intr_config_hook *hook);
 void	config_intrhook_disestablish(struct intr_config_hook *hook);
+void	config_intrhook_oneshot(ich_func_t _func, void *_arg);
 
 #endif /* !_SYS_KERNEL_H_*/